It is the only motorway junction inside a national park, though until the national park was created, the New Forest boundary skirted the junction. Despite being the western terminius of the M27, the junction has three lanes through it, but the A31 to the west is only two lanes. This creates a bottleneck where the 3-lane M27 and 2-lane on-slip merge into the 2-lane A31 in a short distance.

Until the end of the 1970s the junction was unnumbered, with junction numbering beginning at Ower.